1. Field of the Invention
The present invention concerns a method and a control system for producing one or more two-dimensional MR images using a magnetic resonance imaging scanner. Furthermore, the present invention concerns a magnetic resonance imaging apparatus for implementing such a method.
2. Description of the Prior Art
With image processing for orthopedic purposes, the aim is to simplify and improve the diagnostic process, and thereby also accelerate the associated work flow in an examination. Conventionally, in an orthopedic examination, images of a joint are made in different planes in order to be able to make a necessary diagnosis. As an example, in an examination of a knee joint, images are necessary in one plane for the meniscus, in one plane for the cartilage, and in various planes for the various ligaments in the knee region. With the conventional procedure, whereby the planes or layers necessary for the examination are determined based on two-dimensional images, the production of the necessary images for examining a knee joint is extremely time consuming. Furthermore, there is the problem, with a subsequent examination of the same knee joint, of determining the same planes in order to obtain reproducible or comparable results. These problems presently restrict the diagnostic results and limit the efficiency in clinical applications.
The following describes the procedure for such examinations according to the present state of technology.
The joint to be examined is first localized using images of lower resolution. Subsequently, two-dimensional images of a higher resolution are produced, in order to plan out which two-dimensional MR images are necessary for the actual diagnosis. For this purpose, three different perspectives of the joint are imaged by the higher resolution two-dimensional images. These perspectives are planned using the lower resolution images taking the anatomical data into account, so the resulting perspectives generally correspond to the sagittal, coronal, and transversal planes.
In other words, the layers for the necessary two-dimensional MR images are planned out using two-dimensional images. Normally, this results in the MR images necessary for the diagnosis being produced in layers which lie in the sagittal, coronal, or axial planes. The structures, however, that must be examined for an exact diagnosis of the meniscus or cruciate ligament in the knee, for example, do not lie in the sagittal, coronal, or axial plane, but rather, run at an angle to these planes. Furthermore, there are patient dependent anatomical differences, which require the production of the two-dimensional MR images to be tailored to the individual patient. In summary, the two-dimensional MR images produced according to the present state of technology seldom contain the information necessary for an exact diagnosis.
This problem is approached according to the present state of technology, by the patient which is to be examined being placed in a standardized position, and the planning of the layers, so the necessary MR images will be produced based on the experience of the attending technician. The anatomical differences between different patients set tight limits for the process used according to the present state of technology however, such that the resulting diagnosis based on MR images produced in this manner is, to some extent, inexact. Furthermore, reproducibility of the MR images is difficult to achieve, particularly when the MR images which are to be compared are produced by different operators (e.g. doctors).
A further problem, in accordance with the state of technology, is that production of a higher resolution MR image can first commence when the layer is determined in which the MR image is to be recorded. This means that the work flow, with the present state of technology, is sequential for the most part, and a quality check may first be made after the MR image has been produced. This leads to either only limited diagnosis on the basis of the MR images, or repeated planning and production of the MR images, so the examination period is extended for the patient and the doctor.